The invention relates to improvements in torque converters, and more particularly to improvements in torque converters which can be utilized with advantage in the power trains of motor vehicles, e.g., to transmit torque between a rotary output member (such as a crankshaft or a camshaft) of a prime mover (e.g., a combustion engine or a hybrid drive) and the rotary input member of the transmission which drives some or all wheels of the motor vehicle.
As used herein, the term “torque converter” is intended to denote a hydrodynamic or hydrokinetic torque converter comprising a rotary housing, a pump which rotates with the housing, a turbine which can rotate with and relative to the pump, and normally or frequently a stator or guide wheel between the pump and the turbine. Torque converters of such character are known and utilized for many decades and certain presently known torque converters are disclosed, for example, in commonly owned U.S. Pat. Nos. 5,738,198 (granted Apr. 14, 1998 to Walth et al. for “FRICTION ELEMENT FOR USE IN CLUTCHES”) and 5,782,327 (granted Jul. 21, 1998 to Otto et al. for “HYDROKINETIC TORQUE CONVERTER AND LOCKUP CLUTCH THEREFOR”).
The housing of the torque converter is filled with oil or another suitable hydraulic fluid which causes the turbine to turn in response to rotation of the pump. The stator serves to enhance the efficiency of the torque converter. The energy of the hydraulic fluid stream in the turbine entails the generation of torque which is transmitted to the output shaft of the turbine. Such output shaft can constitute the input shaft of the change-speed transmission in the power train of the motor vehicle.
Since the rotary output member of the prime mover (such as the crankshaft of a combustion engine) and the rotary mass which shares the movements of the output member tend to develop torsional vibrations, the torque converter in the power train of the motor vehicle is normally equipped or associated with a shock absorber or damper which is designed to store larger temporary or momentary torsional vibration amplitudes and to transmit them to the transmission when the amplitude of torsional vibrations being transmitted by the engine decreases. This minimizes the overall torsional vibration amplitudes.
A torsional vibration damper can further comprise damping elements which are set up to absorb additional undesirable torsional vibration energy. Still further, the torsional vibration damper can comprise a so-called bypass or lockup clutch which is engaged or closed when the ratio of turbine RPM to pump RPM in the housing of the torque converter is 85% or thereabout. This increases the efficiency of the torque converter to, or close to, 100%. Closing or engagement of the bypass clutch is effected by a flow of hydraulic fluid in the torque converter. Such fluid flow engages or closes the bypass clutch and can constitute the flow which issues between the pump wheel and the turbine wheel or an additional (hydrostatic) stream or flow.
The flow of energy in a turbine damper takes place by way of an inlet or input part to thereupon flow along springs which are provided to transmit energy to an output or outlet part (also called flange). The output part is connected to or is of one piece with a hub which, in turn, transmits energy to the turbine shaft, i.e., to the input shaft of the change speed transmission.
It will be seen that a conventional torque converter for use in the power train of a motor vehicle employs a substantial number of component parts which are installed in the power flow between the turbine and the input shaft of the transmission and which must be capable of transmitting and standing the supplied torque. The quality of such parts (and of the spare parts therefor) must be very high which contributes significantly to the initial and repair cost, especially if the torque converter is to be installed in the power trains of series-produced motor vehicles.